The present application relates to a process for converting organic wastes into a reducing agent-coke substitute (RACS). More specifically, the present application describes a process for producing a reducing agent-coke substitute from a mixed waste material containing organic based materials and economically recoverable metals.
Mixed waste materials contain various concentrations of economically recoverable metals, such as tin, lead, antimony, silver and gold that are comingled with, or an integral part of, organic-based materials, such as paper, latex, wood, plastic, fiber, vinyl scrap and cloth. It can be difficult to recover the desired metals from these mixed waste materials because of the presence of the organic-based materials which can interfere with the recovery of metals under normal processing operations.
Traditionally, mixed waste materials containing organic materials and recoverable metals are processed by destroying the organic materials via combustion in a furnace at temperatures from about 800-1200° F. and then recovering the remaining metals by smelting and refining. In order to process the organic materials without having the materials combust explosively, the furnace temperature must be lowered from the normal operating temperatures of 1800° F. or higher to room temperature. The organic-containing materials are slowly heated to remove the organic matter in the composition and then the temperature is raised to the normal operating temperature. Lowering the furnace temperature to process organic materials results in slower and inefficient processing. Furthermore, in some cases burning embers may be entrained in the off-gas and cause the bags in the baghouse to catch fire, thereby causing production stoppages, expensive repairs, and inadvertent releases of heavy metals to the environment.
Metals can be recovered from metal oxides using coke as a reducing agent. The present application is directed to a process for handling mixed waste materials in an efficient manner to produce a reducing agent-coke substitute that can be utilized in place of coke during the recovery of metals from metal oxides. In accordance with certain aspects, the resulting reducing agent may be at least 50% as effective and, in some cases, even more effective than coke.